package com.dbh.alg.algorithm.hot100.图论;


import java.util.LinkedList;
import java.util.Queue;

/**
 * @author 董帮辉
 * @date 2025/7/26
 * <p>
 * 给你一个由 '1'（陆地）和 '0'（水）组成的的二维网格，请你计算网格中岛屿的数量。
 * <p>
 * 岛屿总是被水包围，并且每座岛屿只能由水平方向和/或竖直方向上相邻的陆地连接形成。
 * <p>
 * 此外，你可以假设该网格的四条边均被水包围。
 * <p>
 *
 *
 * 示例 1：
 * <p>
 * 输入：grid = [
 *   ["1","1","1","1","0"],
 *   ["1","1","0","1","0"],
 *   ["1","1","0","0","0"],
 *   ["0","0","0","0","0"]
 * ]
 * 输出：1
 * 示例 2：
 * <p>
 * 输入：grid = [
 *   ["1","1","0","0","0"],
 *   ["1","1","0","0","0"],
 *   ["0","0","1","0","0"],
 *   ["0","0","0","1","1"]
 * ]
 * 输出：3
 * <p>
 *
 * 提示：
 * <p>
 * m == grid.length
 * n == grid[i].length
 * 1 <= m, n <= 300
 * grid[i][j] 的值为 '0' 或 '1'
 *
 **/
public class Leetcode200_岛屿数量 {

    /**
     * 深度优先搜索
     * @param grid 数组
     * @return 岛屿数量
     */
    public int numIsLand(char[][] grid) {
        if (grid == null  || grid.length == 0){
            return 0;
        }

        int m = grid.length;
        int n = grid[0].length;
        int ans = 0;
        for (int r = 0; r < m; r++) {
            for (int c = 0; c < n; c++) {
                if (grid[r][c] == '1') {
                    ans++;
                    dfs(grid, r, c);
                }
            }
        }
        return ans;
    }

    private void dfs(char[][] grid, int r, int c) {
        int m = grid.length;
        int n = grid[0].length;
        if (r < 0 || c < 0 || r >= m || c >= n || grid[r][c] == '0') {
            return;
        }
        grid[r][c] = '0';
        dfs(grid, r - 1, c);
        dfs(grid, r + 1, c);
        dfs(grid, r, c - 1);
        dfs(grid, r, c + 1);
    }


    /**
     * 广度优先搜索
     * @param grid 数组
     * @return 岛屿数量
     */
    public int numIsLand2(char[][] grid) {
        if (grid == null  || grid.length == 0){
            return 0;
        }
        int m = grid.length, n = grid[0].length, ans = 0;
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (grid[i][j] == '1') {
                    ans++;
                    grid[i][j] = '0';
                    Queue<Integer> queue = new LinkedList<>();
                    queue.add(i * n + j);
                    while (!queue.isEmpty()) {
                        int id = queue.poll();
                        int row = id / n;
                        int col = id % n;
                        if (row - 1 >= 0 && grid[row-1][col] == '1') {
                            queue.add((row - 1) * n + col);
                            grid[row-1][col] = '0';
                        }
                        if (row + 1 < m && grid[row+1][col] == '1') {
                            queue.add((row + 1) * n + col);
                            grid[row+1][col] = '0';
                        }
                        if (col - 1 >= 0 && grid[row][col-1] == '1') {
                            queue.add(row * n + col - 1);
                            grid[row][col-1] = '0';
                        }
                        if (col + 1 < n && grid[row][col+1] == '1') {
                            queue.add(row * n + col + 1);
                            grid[row][col+1] = '0';
                        }
                    }
                }
            }
        }
        return ans;
    }
}
